Input Kafka Mapper Output 
{
  "timestamp":"2021-06-08T12:17:27Z",
    "labels":{
    "instance":"100.96.2.131:8080",
    "amf_nas_non_delivery_indication":" value",
    "app":"amf",
    "kubernetes_namespace":"meta323",
    "job":"kubernetes-namespace-pods",
    "pod_template_hash":"549dc5ff4d",
    "kubernetes_pod_name":"fusion-5g-c-ae701-696lz-5g-core-amf-549dc5ff4d-jxcrb",
    "release":"fusion-5g-c-ae701-696lz",
    "__name__":"nf_counter_stat"
  },
  "name":"nf_counter_stat",
  "value":"0"
}
 
{
    "metricType":"5G-Core",
    "instance":"Metaswitch-5g-core-metrics",
    "properties.entityName":"$.labels.app",
    "properties.entityType":"app",
    "processedTimestamp": "$.timestamp.transform_date(\"yyyy-MM-dd'T'HH:mm:ss'Z'\")",
    "metrics.$['name']":"$.value",
    "type":"Kafka-Collector",
    "properties.dataSource":"$.labels.instance",
    "properties.deviceName":"$.labels.kubernetes_pod_name",
    "timestamp":"$.timestamp.transform_date(\"yyyy-MM-dd'T'HH:mm:ss'Z'\")",
    "properties.deviceType":"$.labels.job",
    "tags":"$.labels"
}
 
{
    "instance":"Metaswitch-5g-core-metrics",
    "metricType":"5G-Core",
    "timestamp":1623179847000,
    "processedTimestamp":1623179847000,
    "type":"Kafka-Collector",
    "metrics":{
        "nf_counter_stat":0.0
    },
    "properties":{
        "deviceType":"kubernetes-namespace-pods",
        "entityName":"amf",
        "entityType":"app",
        "dataSource":"100.96.2.131:8080",
        "deviceName":"fusion-5g-c-ae701-696lz-5g-core-amf-549dc5ff4d-jxcrb"
    },
    "tags":{
        "app":"amf",
        "kubernetes_namespace":"meta323",
        "instance":"100.96.2.131:8080",
        "__name__":"nf_counter_stat",
        "release":"fusion-5g-c-ae701-696lz",
        "amf_nas_non_delivery_indication":" value",
        "pod_template_hash":"549dc5ff4d",
        "job":"kubernetes-namespace-pods",
        "kubernetes_pod_name":"fusion-5g-c-ae701-696lz-5g-core-amf-549dc5ff4d-jxcrb"
    }
}
The explanation for all the lines in the Kafka Mapper is covered in Example 1. There is one line which is not covered in example 1 and can be highlighted: 
"timestamp":"$.timestamp.transform_date(\"yyyy-MM-dd'T'HH:mm:ss'Z'\")"
The above line demonstrates the use of a custom function for identifying the format of the timestamp in the incoming data. The $.timestamp identifies the field in the incoming data that contains the timestamp, and the transform_date is the function call that takes the timestamp format as argument, which is a string. Java timestamp library format are accepted. 
{
  "timestamp":"$.timestamp.transform_date(\"yyyy-MM-dd'T'HH:mm:ss'Z'\")"
}
would resolve to the output
{
  "timestamp":1623179847000
}